Protein BIOKIMIA 202198 BIOKIMIA Protein Protein terbentuk atas

Protein BIOKIMIA 2021/9/8 BIOKIMIA

Protein • Protein terbentuk atas beberapa AA, hampir semua AA memiliki karbon asimetrik (α-karbon) yg mengikat 4 gugus yaitu: – Karboksil – Amino –R – hidrogen 2021/9/8 BIOKIMIA

Amino acid: Basic unit of protein R NH 3 + C Amino group H Different side chains, R, determin the COO properties of 20 Carboxylic acid group amino acids. An amino acid

20 Amino acids Glycine (G) Alanine (A) Valine (V) Isoleucine (I) Leucine (L) Proline (P) Methionine (M) Phenylalanine (F) Tryptophan (W) Asparagine (N) Glutamine (Q) Serine (S) Threonine (T) Tyrosine (Y) Cysteine (C) Lysine (K) Arginine (R) Histidine (H) Asparatic acid (D) Glutamic acid (E) White: Hydrophobic, Green: Hydrophilic, Red: Acidic, Blue: Basic

Lanjutan • AA dianalisis menggunakan AAA, dg syarat diketahui polaritasnya sekaligus dilihat kandungan gugus R, p. H=7 1. Gugus R sama sekali tdk polar (hidrofobik), cont. alanin, fenilalanin, triptofan 2. Gugus R sangat polar (hidrofilik), cont. sistein, tirosin 2021/9/8 BIOKIMIA

Lanjutan 3. AA gugus R bermuatan negatif (asam), cont. aspartat, as. glutamat 4. AA gugus R bermuatan positif (basa), cont. histidin, arginin 2021/9/8 BIOKIMIA

Karakteristik AA • Zwitter ion (ion ganda), bisa bermuatan positif & negatif • Bipolar, bisa berperan sebagai asam dan basa 2021/9/8 BIOKIMIA

Asam Amino • AA merupakan pembentuk protein yg terikat pd ikatan polipeptida. • Ciri khas protein akan mengikuti ciri khas AA pembentuknya. 2021/9/8 BIOKIMIA

Lanjutan • Berdasarkan gugus & rumus bangun AA terbagi atas: 1. Alifatic side chain; glisin, alanin, valin 2. Hydroxylic side chain; threonin 3. Carboxylic side chain; amida 4. Aromatic side chain; as. glutamat 5. Sulfur containing side chain; metionin 6. Basic side chain; arginin, lisin 7. Imino acid side chain; prolin, hydroxyprolin 2021/9/8 BIOKIMIA

Bentuk &Sifat Fisik Protein 2021/9/8 BIOKIMIA

1. GLOBULAR • Berbentuk bulat • Rantai berlipat-lipat • Larut dlm sistem larutan termasuk air & mudah terdifusi CONTOH: Insulin; hemoglobin; enzim; antibodi 2021/9/8 BIOKIMIA

2. SERABUT • Rantai polipeptida panjang, memanjang pd satu sumbu • Peranannya bersifat struktural & pelindung CONTOH: Hair; wool; nails; skin 2021/9/8 BIOKIMIA

Bentuk &Struktur Protein 2021/9/8 BIOKIMIA

Primary Structure of Proteins The particular sequence of amino acids that is the backbone of a peptide chain or protein Ala-Leu-Cys-Met 14

Proteins are linear polymers of amino acids R 1 R 2 NH 3＋ C COO ＋ ー ー H H A carboxylic acid H 2 O condenses with an amino group with the release of a water H 2 O R 1 R 2 R 3 NH 3＋ C CO NH C CO H A F Peptide bond G N S Peptide bond H T D K G H S A The amino acid sequence is called as primary structure

Secondary Structure – Alpha Helix • Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape • Held by H bonds between the H of –N-H group and the –O of C=O of the fourth amino acid along the chain • Looks like a coiled “telephone cord” 16

Secondary Structure – Beta Pleated Sheet • Polypeptide chains are arranged side by side • Hydrogen bonds form between chains • R groups of extend above and below the sheet • Typical of fibrous proteins such as silk 17

Secondary Structure – Triple Helix • Three polypeptide chains woven together • Glycine, proline, hydroxy proline and hydroxylysine • H bonding between –OH groups gives a strong structure • Typical of collagen, connective tissue, skin, tendons, and cartilage 18

Basic structural units of proteins: Secondary structure α-helix β-sheet Secondary structures, α-helix and β-sheet, have regular hydrogen-bonding patterns.

Tertiary Structure • Specific overall shape of a protein • Cross links between R groups of amino acids in chain disulfide –S–S– + ionic –COO– H 3 N– H bonds C=O HO– hydrophobic –CH 3 H 3 C– 20

Quaternary Structure • Proteins with two or more chains • Example is hemoglobin Carries oxygen in blood Four polypeptide chains Each chain has a heme group to bind oxygen 21

Three-dimensional structure of proteins Tertiary structure Quaternary structure

Hierarchical nature of protein structure Primary structure (Amino acid sequence) ↓ Secondary structure （α-helix, β-sheet） ↓ Tertiary structure （Three-dimensional structure formed by assembly of secondary structures） ↓ Quaternary structure （Structure formed by more than one polypeptide chains）

Berdasar ik. peptida &ik. lainnya 1. PROTEIN SEDERHANA Yaitu hanya mengandung α-AA saja Cont. Albumin, globulin, glutein, histon 2. PROTEIN KONJUGASI Yaitu disamping mengandung AA jg komponen lain yg jika dihidrolisa menghasilkan gugus yg dinamakan gugus prostetik Cont. lipoprotein, glikoprotein, metaloprotein 2021/9/8 BIOKIMIA

Fungsi Protein 2021/9/8 BIOKIMIA

Fungsi Biologis protein 1. ENZIM; tripsin, lipase, protease 2. PROTEIN TRANSFER; membawa sesuatu utk proses metabolisme, ex. hemoglobin 3. NUTRIENT; pembawa zat gizi, ex. kasein 4. KONTRAKTIL; utk bergerak, ex. Aktin &miosin 2021/9/8 BIOKIMIA

Fungsi Biologis protein 5. STRUKTURAL; membentuk struktur ex. kolagen 6. PERTAHANAN; ex. antibodi 7. PENGATUR (REGULATORY PROTEIN); ex. Insulin (mengatur kadar glukosa dlm darah) 2021/9/8 BIOKIMIA

Lain-lain 2021/9/8 BIOKIMIA

Protein Hydrolysis • Break down of peptide bonds • Requires acid or base, water and heat • Gives smaller peptides and amino acids • Similar to digestion of proteins using enzymes • Occurs in cells to provide amino acids to synthesize other proteins and tissues 29

Hydrolysis of a Dipeptide 30

Denaturation Disruption of secondary, tertiary and quaternary protein structure by heat/organics Break apart H bonds and disrupt hydrophobic attractions acids/ bases Break H bonds between polar R groups and ionic bonds heavy metal ions React with S-S bonds to form solids agitation Stretches chains until bonds break 31

Applications of Denaturation • • • Hard boiling an egg Wiping the skin with alcohol swab for injection Cooking food to destroy E. coli. Heat used to cauterize blood vessels Autoclave sterilizes instruments Milk is heated to make yogurt 32

TERIMA KASIH 2021/9/8 BIOKIMIA